This invention relates to computer address computation operations. More particularly, this invention relates to address computations which are needed to support the fetching of individual operands, which may range in length up to multi-byte, from main memory.
There exists any number of different methods for storing and transferring information into and out of computer memory. However, in larger business-oriented systems it is quite common to employ hard disk memories for the bulk of the stored information in combination with the electronic main memory resident within the computer itself. Information is normally initially entered onto the hard disk, and it is identified by a virtual address which consists of a frame identification (FID) and a displacement within the identified frame. This FID plus a displacement uniquely define a virtual address for each block of information on the hard disk. However, in order to be useful to the CPU of the computer system, the information must be read into the high-speed main memory of the computer system, which is normally done by an internal management function which assigns the information blocks to available positions within the main memory. These main memory positions must also be defined and identified in order that the information can be used by the CPU, and to this end means must be provided to uniquely identify these information blocks within the main memory.